A bistable display element in a liquid crystal (LC) display system using electrophoretic particles remains in a predetermined cell state for a period of time without the need for power. The degree of bistability may be controlled by chemical or electrical modification of the suspended electrophoretic particles. Nematic LC molecules are oriented in substantially parallel lines in a mesomorphic phase. Existing bistable LC display elements typically have fixed alignment on at least one interior surface and a switching alignment on the other interior surface of a display element.
Before an electric field is applied to an LC display element, the orientation of the liquid crystal molecules is determined by the alignment on the interior surfaces or alignment layers of the LC cell. Alignment layers can separate the LC from the electrodes or glass substrate and give a preferred direction of orientation for the LC molecules. Nematics have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field. An aligned nematic has the optical properties of a uniaxial crystal and this makes them extremely useful in LC displays.
Prior systems may have applied microstructure gratings on both interior surfaces of their bistable devices. Driving this type of device can be complicated, and the construction of the microstructures can be a manufacturing challenge. Other bistable display element configurations rely on polarizers for their optical effect and only have microstructure on one interior surface of the device. As such, it has been difficult to achieve full horizontal to vertical switching of the LC molecules.